The present invention relates to a tire manufacturing method and a machine, and particularly to method and a machine for forming a green-case by a first forming machine.
In the first forming machine, beads are driven on portions near both ends of a ply applied on a drum and the both ends are folded back about the beads by means of bladders to form a green-case. The bead setter is required to be driven with a thrust higher than 4 tons to drive the beads and fold back the ply, and therefore in conventional bead setters, hydraulic cylinders have been used.
For example, a hydraulic pump is operated by a large capacity electric motor of 15 Kw or more and the hydraulic cylinder is driven by oil pressure caused by the hydraulic pump to move a bead holder.
The oil pressure of the hydraulic cylinder can be changed barely in two steps of high and low, and it is impossible to set thrust and moving speed separately. Therefore moving speed is sacrificed to obtain a necessary thrust and the production efficiency is low. Since thrust can not be adjusted step by step, it is impossible to correspond with various tire sizes.
In the case where the hydraulic cylinder is operated with high oil pressure, the thrust is too large for some tire sizes and the beads are apt to slip off when the beads are driven or the ply is folded back, therefore there is a problem that quality of the tire deteriorates owing to the slipping off of the beads.
On the other hand, in the case that the hydraulic cylinder is operated with low oil pressure, there is a fear that the thrust for driving the beads or folding back the ply is insufficient and it is impossible to cope with various tire sizes.
Since the hydraulic pump is driven by the electric motor of large capacity, electric power consumption is large. It is necessary to inspect the hydraulic pump periodically to confirm the oil amount, therefore many man-hours are required for maintenance and the work is troublesome. The mechanism becomes complicated because a hydraulic circuit must be constituted, and sometimes an additional cooling fan is required to avoid increase of oil temperature resulting in high cost.